L. P. Lima

Psim mathematical tools to simulate pem fuel cells including the power converter

This paper presents a mathematical model for proton exchange membrane fuel cells (PEMFCs) taking into account the basic electrochemical equations but including the boost power converter. This approaching is suitable for design and simulation of power electronics systems with embedded FCs as power supplies. The simplified model uses the Kirchoffs Voltage Law (KVL) applied to the conventional electric equivalent model of PEMFCs. This work is fully implemented in PSimTM as a general mathematical model and referred to literature data including the Boost converter, mostly used as the power interface for FCs. In this way, the model is fully evaluated by viewing the interface just as a power converter.

Advanced High Frequency AC Microgrid with integrated power quality conditioning capability

This paper presents a high frequency AC (HFAC) microgrid with power quality conditioning capacity, as an alternative energy conversion for integration of renewable energy sources in a distributed generation system. It is shown that successful implementation of any HFAC microgrid relies on the best utilization of the source and integrating bus, which can be accomplished by using a unified power quality conditioner (UQPC). The UPQC can simultaneously compensate for current and voltage harmonics and also for reactive power. Its controller is based on the modified instantaneous p-q theory and the results obtained show that this conditioner can be effectively used to improve the quality of power systems.

Reduction of electrical load for air conditioning by electronically controlled geothermal energy

This paper describes the design steps of a geothermal system for air conditioning to reduce electricity consumption in residential and small business ambient. To do that it is used surface geothermal energy as one of the heating sources. The geothermal surface is renewable, clean, universal, silent and odorless relying on the circulation of a refrigerant within a pipe hose buried with the aid of a very small size pump, so that the earth absorbs heat in the summer and supplies it to the rooms in the winter. There is a controlled exchange of heat between the one removed from the grounds by a water circulating radiator and a room ventilation system. That is, if the temperature inside the building is above the earth temperature it will tend to level off the temperature with that from ground. A prototype of heat exchanger and electronic control system without any heat pump was built using a hill climbing algorithm to optimize the water pump speed and this heat exchanging system.

FC and PV emulation by buck converter based on experimental VxI curves and dynamic response

This paper presents an emulation of fuel cell and photovoltaic modules based on the buck converter as a replacement of actual power sources for bench tests. This approach is suitable for power electronic designs involving power converters to interface source and DC loads or source and mains grid, without having available the real source. The output voltage of the buck converter is referred to lookup tables/equations with experimental data from actual sources under load variation to determinate the biasing curves and dynamic response. To validate the results, a comparison between simulated and practical results obtained from laboratory test with actual sources is performed. The energy source emulations with buck converters is a simple, safe, versatile, and effective way of physically representing DC sources for various laboratory tests.

Surface geothermal energy applied to low cost and low power consumption residential air conditioning

The operation of an air-conditioning system, completely powered by geothermal energy, with no other external energy input and no heat pump is described in this paper. This geothermal system can contribute to the reduction of electricity consumption in residences and small businesses, and can retrofit any installation, since it is a surface geothermal energy installation. That is possible because soil temperature, to a certain depth, has a constant temperature throughout the year, with a large mass and heat capacity. Practical tests can be easily conducted with water and underground heat exchangers. This system is designed with a coolant circulating within a serpentine driven by a small hydraulic pump. If the temperature inside the residence is lower or higher than the soil temperature, there is heat exchange between the residence ambient and the soil. Therefore, the surface geothermal energy is used to warm-up or cool-down the room ambient. The prototype described in this paper was implemented with an electronic control to maximize the performance of the heat exchangers. Experiments were made during four months in the winter and in the summer.

Integration of alternative sources of energy as current sources

This work proposes an integration of alternative energy sources having the different generating modules connected as current sources. These sources were configured to inject current into a common DC bus. This feature avoids current circulation among sources due to the voltage differences, reducing the stress in the individual generators. A battery bank is a system part, used as an energy accumulator for periods when there is primary energy depletion. The bus voltage is controlled by modulation of a secondary load in parallel with the main load. A DC-DC Boost converter connects each primary source to a common bus, except for the storage system that uses a DC-DC Buck-Boost converter. Finally, it is presented a mathematical analysis through simulated results to show the sources behavior and overall performance when turned into current sources.

Inclusion of the start-up effect in the electronic modeling of proton exchange membrane fuel cells

This paper presents a study regarding to modeling proton exchange membrane fuel cells (PEMFC) using an improved electronic model. The original model is not able to reproduce the FC initialization (or start-up) effect FC. So, in this work a proposal to include this effect is accomplished. To validate this study, the results are compared with obtained data from manufacturers and previously published results in literature. These data are collected for a 500W BCS PEMFC stack.